Grumman has a design already tested. All that needs to be done is to update the flight computer with a bit more memory to eliminate those pesky 1201 alarms on final descent.
That design presumes a 1960s US industrial base, which no longer exists.
The real problem, here, is that we quit going to the Moon back in 1972. This means we have to start from scratch in many respects. We know it can be done, but we still have to (re)invent things. We should have been flying around the Earth-Moon system, and beyond, all these years, and gradually improving our spacecraft. We should have spacecraft right now, with evolutionary heritage back to Apollo ... but we don't. We have a cradle-to-grave welfare state, instead. That's what the democRATs wanted. Can't have Whitey on the Moon; that's racist.
And upgrade from windows xp.